This invention relates to apparatus and method for reducing or removing biofilm. The target biofilm may be on a wound site particularly a wound site that is being debrided to remove necrotic tissue. Alternatively, the target biofilm may be on a prosthetic device or component that is either in situ in a patient, or removed from the patient for cleaning and re-implantation.
Chronic wound infection represents a significant healthcare problem worldwide. Often the end objective of wound healing is the objective for new therapeutic options. Yet chronic wounds compromise a number of different and complex conditions that each interferes with the healing process. For example, a chronic wound can comprise necrotic tissue in need of debridement, bacterial infection in need of antimicrobial agents and compromised vasculature that impedes the normal healing process.
One element of the chronic wound infection condition that impedes healing is the formation of biofilm. Biofilm is the result of planktonic bacteria forming together and secreting exopolysaccharide (EPS) to adhere and protect the colonizing community. At the height of formation, EPS can make up between 75-90% of the total biofilm composition (Regt). Biofilm inhibits healing by creating an optimal condition for bacteria to grow, while simultaneously preventing antimicrobial agents from direct access to bacteria.
Methods to remove biofilm include ultrasonic debridement, topical antimicrobials, suction, and surface cleansing. Each of these methods alone treat an aspect of biofilm. For example, ultrasonic debridement of wounds has proven to be the most effective mechanism in disrupting and debulking a majority of the biofilm formation. Yet even in this preferred method, biofilm debris can be left behind to propagate. Suction alone has not proven to be effective in removing biofilm, and can potentially interfere with the operation of other methods like ultrasonic debridement if applied simultaneously.
U.S. Pat. No. 7,608,054 to Soring et al. describes a medical treatment apparatus that combines an ultrasound sonotrode with a suction sheath. The fixed position between the tip of the suction and the tip of the sonotrode only allows for one simultaneous operation. In particular this approach is limited due to the potential interference of the suction tip during the ultrasonic debridement operation.
U.S. Pat. No. 7,522,955 B2 to Rontal et al. describes a method and apparatus for ultrasonic cleaning of biofilm coated surfaces for sinus cavities within a human head. The method describes an ultrasonic application in combination with irrigation and suction that is designed to not remove any of the surrounding underlying tissue. This differs significantly from an ultrasonic debridement of a wound bed, which requires the removal of tissue in combination with biofilm. Thus the ultrasonic probe needs to operate in a cavitation mode at the surface of a wound, causing destruction of the biofilm.
Methods of mechanical removal of biofilm in wounds alone have proven to be inadequate. What does not exist and what would be beneficial to the market is a method to remove biofilm and prevent it from reforming in order to allow wounds to heal.
A particular kind of wound in which biofilm may form is at a site of prosthesis implantation. It is not uncommon for infection to crop up at sites of prosthetic implants. Frequently the prostheses must be removed in whole or in part to enable cleaning of the implantation site. In addition, the prosthetic parts, which are generally reinserted into the patient must be cleaned of biofilm.